Dr. Malin Pinsky1, Dr. Anne Maria Eikeset2, Dr. Douglas McCauley3, Dr. Jonathan Payne4, Dr. Jennifer Sunday5
1Rutgers University, New Brunswick, United States, 2University of Oslo, Oslo, Norway, 3University of California Santa Barbara, Santa Barbara, United States, 4Stanford University, Stanford, United States, 5McGill University, Montreal, Canada
Both marine and terrestrial fauna have been impacted by warming, but an explicit comparison of physiological sensitivity between marine and terrestrial realms has been lacking. Although populations living closer to their upper thermal limits tend to decline more when faced with warming, assessing proximity to these limits has been challenging in part because extreme temperatures frequently drive demographic responses and because fauna can use local thermal refugia to avoid extremes. Here, we calculated the difference between a species’ acute upper thermal limit and its extreme hot hourly body temperature in the coolest available microhabitat for 88 marine and 294 terrestrial ectotherms as an index of excess thermal tolerance. On land, the species with the smallest thermal safety margins were at mid-latitudes where the hottest hours occurred. Marine species with the smallest margins were instead near the equator. Marine ectotherms had smaller margins than terrestrial ectotherms across all latitudes, but only if terrestrial species could access thermal refugia. We also found that warming-related local extirpations have been twice as common in the ocean as on land, consistent with population-level consequences of less thermal safety at sea. Higher sensitivity to warming and faster colonization would suggest that future warming will drive more frequent extirpations and species turnover in the ocean. In contrast, terrestrial species appear more vulnerable to loss of access to thermal refugia, making habitat fragmentation and land use change a critical driver of species loss.
Malin is an associate professor at Rutgers University in New Jersey, United States, where he leads a research group focused on the impacts of climate variability and climate change on marine species distributions, community composition, and rapid evolution.